Pressure retainer and relief device



Sept. 2, 1930. w, RANKlN 1,774,946

PRESSURE RETAINER AND RELIEF DEVICE Original Filed July 11, 3.927

InvenTor' William K.Rclnkir\, y Hi5 Afl'or'ney.

Patented Sept. 2, 1930 UNITED STATES PATENT} OFFICE mm X. RANKIN, OF SCOTIA, NEW YORK, ASSIGNOB TO GENERAL ELECTRIC OOH- PANY, A CORPORATION OF NEW YORK PRESSURE RETAINER AND BELIEF DEVICE Application filed July 11, 1927, Serial No. 204,687. Renewed May 22, 1930.

My invention relates to closed casings which are adapted to contain electrical apparatus and in which pressures may be produced sufiicient to cause rupturing of the 5 vessels. My invention relates particularly to a pressure-retaining and rellef device for suc acaslng.

A breakdown of the insulation of the ap paratus in the vessel, particularly when oil 10 is used as an insulating medium and,in the case of an oil switch, a failure of the switch to cause a complete interruption of the circuit may be followed by the sudden generation of a sufficient amount of gas through 1 the disintegration of the oil to burst the casing with the attendant scattering of hot oil and gas. To safeguard against such acci-.

- dents attempts have been made to provide the enclosing'casing with a pressure relief open- '0 ing closed by a flat plate of metal or of a brittle material such as glass. With such diaphragms difficulty has been experienced in constructing them to give way with the desired uniformity whereby they might be relied upon always to relieve the pressure in the casing at and only at a specific pressure value. My invention has for its object therefore the provision of an improved pressureretaining and relief device for an enclosing o casing with which the aforesaid objections 'are avoided and with which approximately ing the oil immersed contacts and comprising the tank 1 and the cover 2 to which it is firmly secured. Insulator bushings 3 are supported by the cover and to them are secured the fixed contacts within the tank. For the purpose of simplifying the drawing I have omitted the showing of any mechanism for operating the movable contacts or even an enclosing casing for such mechanism which usually is mounted above or in the cover.

To prevent the throwing of oil the casing comprising the tank 1 and cover 2 preferably is tight except for a small bleed hole or for an opening leading to a cooling and separating chamber such for example as the well known gravel baflie. In either case the casing is constructed to withstand the maximum pressure developed therein due to the normal operation of the switch. In the event of an insulating breakdown in the casing or of a failure of the switch to completely interrupt the circuit when the enormous quantity of gas suddenly generated would endanger the casing I have provided the relief means now to be described.

In the central portion of the cover I have shown a relatively large relief opening 5 in which is preferably secured a member such as a ring or nipple 6 projecting outward from the cover and having at its outer end an in- 75 ternal flange 7. The opening in the nipple is normally closed by the diaphragm or plate 8 which is concavo-convex in form and is mounted within the nipple with its edge engaging the same and the flange, the diaphragm being arranged with its convex face turned inward or-toward the pressure. The cover of the casing may be constructed so that the diaphragm is mounted directly in the opening in the cover, but replacement of the diaphragm is then more difficult unless a part of the cover is made removable for the purpose. It will be apparent that the diaphragm may be secured at the outer end of g a pipe or the like extending some distance from the casing without departing from my invention. I prefer to construct the plate of a ductile metal such for example as annealed copper and I also prefer it to have a uniform curvature, spherical for example with a radius of curvature substantially equal to the diameter of the plate. As so shaped and proportioned, calculation of its dimensions for the relief of specific pressures is simplified since it permits the use of a simple formula such as P KT 17 where P is the maximum pressure which the plate will withstand, K is a constant depending upon the material used, T is the thickness and D is the diameter. The plate having been attached to the nipple in any suitable manner, such as by soldering, functions in resisting the internal pressure in the manner of a dome or arch, the radial thrust being taken by the side wall of the nipple and the upward thrust being taken by the flange '7. At the instant the critical pressure is passed the curvature of the plate reverses and having reversed, the plate is easily pushed past the flange 7. Being of light construction, reversal and discharge of the plate takes place with great speed once the plate begins to deform. I have found by actual test that measured pressures at which such diaphragms give way follow very closely the calculated rupture values in this respect being in marked distinction to the results obtained with flat diaphragms. Replacement of the diaphragm is readily effected by first unscrewing the nipple and inserting a new diaphragm therein or inserting a new nipple with attached diaphragm. It is desirable, particularly in the case of an indoor breaker to provide suitable means for carrying off the gas and oil discharged through the nipple to a remote point where they may not endanger the attendants, the building or other apparatus therein but as such means forms no part of my present invention it has not been illustrated.

Although I have chosen to illustrate my invention as applied to an oil switch it is also applicable to other forms of electrical apparatus enclosed in casings as for example transformers. The particular embodiment described above is illustrative only of my invention and it will be apparent that various modifications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A pressure retainer and relief device comprising a concavo-convex plate and a separate supporting member surrounding the plate and engaging it at its edge, said plate being arranged with its convex face toward the pressure and constructed to be reversed and blown from the supporting member in response to a predetermined degree of pressure.

2. A ressure retainer and relief device comprising a circular concavo-convex plate and a separate supporting member surroundin; the plate and engaging the edge thereof,

said plate being arranged so that the pressure engages the convex face thereof and be ing constructed to be reversed and blown free of the supporting member in response to a predetermined degree of pressure.

3. A pressure retainer and relief device comprising a circular concavo-convex plate and a separate supporting member therefor, said member having a portion encircling the edge of the plate and a portion extending radially inward thereof at the concave side of the plate, said plate being arranged with its convex face toward the pressure.

4. A casing apt to have high pressure developed therein due to electrical effects and having a pressure relief opening therein and means normally closing said opening to confine the pressure comprising an inwardly curved concavo-convex plate adapted in response to a predetermined pressure in the casing to have its curvatures reversed and to be blown from the opening.

5. A casing enclosing electrical apparatus, a breakdown of which may cause a dangerously high pressure in the casing, said casing having a pressure relief opening, means forming a discharge passage communicating with said opening, and a concavo-convex plate normally closing said passage, said plate being convex inwardly and said means being constructed to engage the edge of the plate outwardly and circumferentially thereof.

6. A casing subject to internal pressure having a member forming a discharge passage in communication with the interior of said casing, a separate coneavo-convex sheet metal plate enclosed by said member, said plate being convex inwardly and said member being constructed to engage the edge of the plate outwardly and cireumferentially thereof.

7 A casing enclosing electrical apparatus having a pressure relief opening therein, a spherically curved copper plate, and a flanged member communicating with said opening and engaging the edge of the plate outwardly and circumferentially thereof, said plate being arranged with its convex face inward and being adapted in response to a predetermined pressure to reverse and be blown bodily from the casin 8. A switch enclosing casing constructed ,to withstand pressures produced therein due to normal operation of the switch and to effect a substantially instant release of dangerously high pressures therein comprising a top having a discharge passage therethrough, .a separate concavo-convex ductile metal plate closmg said passage and arranged with its convex side toward the interior of the casing and retaining means for said plate engagin theedge, portion thereof circumferentiali y and outwardly, whereby upon the 10 occurrence of a predetermined high pressure in the casing the plate has its curvature reversed and 1s bodily blown free of the retaining means.

' In witness whereof, I have hereunto set 15 my hand this 7th day of July, 1927.

WILLIAM K. RANKIN. 

